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<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <link rel="stylesheet" href="./css/bootstrap.min.css">
  <style>
    .row div{
      border:  1px solid #000;
      height: 40px;
      text-align: center;
      line-height: 40px;
    }
  </style>
</head>
<body>
  <div class="container">
    <div class="row">
      <div class="col-lg-6">1</div>
      <div class="col-lg-6 row">
        <div class="col-lg-6">1</div>
        <div class="col-lg-6">1</div>
      </div>
    </div>
  </div>
</body>
</html>